430 
sample, then the low use must be due to 
low palatability rather than lack of 
availability, for this species is one of the 
top-ranking seed producers, as shown by 
a 1941 study (Low & Bellrose ms.). 
River bulrush, Scirpus fluviatilis, a 
coarse, dominant marsh plant, frequent- 
ly forms dense beds of 50 to 700 acres in 
the Illinois River valley. Only rarely in 
this area does it fruit, and then only in 
small patches; seeds are seldom avail- 
able for food. This circumstance ac- 
counts for the fact that although river 
bulrush formed over 26 per cent of the 
vegetation for the 3-year study period, 
its seed accounted for only 0.50 per cent 
of the uncultivated plant parts con- 
sumed by waterfowl; its index value for 
the 3-year period is 0.02, table 3. At 
Lake Chautauqua, in 1938, when river 
bulrush beds produced more than the 
usual amount of seed, the index value of 
this plant for the area was 0.23. 
Since river bulrush covers extensive 
areas that might well be occupied by 
more valuable food producers, it must 
be regarded as one of the most perni- 
cious weeds in many waterfowl habitats 
of the Illinois River valley. 
American lotus, Ne/umbo /utea, fig. 
15, is next to river bulrush in abundance 
in lakes adjacent to the Illinois River. 
Unlike this bulrush, however, lotus pro- 
duces a fair amount of seed. Yet its 
index rating 1s 0.02, table 3, the same as 
river bulrush. Its slight value as a 
duck food and its dominance over many 
other aquatic plants of greater value 
make this species a weed in the migra- 
tory waterfowl habitats of the Illinois 
River valley. 
Its low value as a duck food plant 
during October and November must be 
attributed to the unpalatability of the 
hard, nutlike seeds. Field observations 
indicate that before the seeds fully 
ripen, in late August and early Septem- 
ber, wood ducks feed extensively on 
them. At that time the pericarp and 
cotyledons of the seed are soft. 
Marsh mallow, Hibiscus militaris, 1s 
not generally regarded as a waterfowl 
food plant. However, in the 3-year in- 
vestigation period it averaged 0.01 per 
cent of the vegetation of the marshes 
studied, table 3, and a few seeds were 
consumed by ducks. 
Ittinoris NATURAL History SURVEY BULLETIN 
Vol. 22, Art. 
Southern naiad, Najas guadalupen- 
$15, 18 apparently a poor duck food in the 
Illinois River valley. While it formed 
0.12 per cent of the vegetation on the 
areas studied, table 3, only a smattering 
of seeds was found in the gizzards 
analyzed. Martin & Uhler (1939), in 
commenting on the value of the north- 
ern and southern naiads in the country 
as a whole, term them excellent duck 
foods. 
Wild rice, Zizania aquatica, fig. 16, is 
often regarded as the food supreme for 
waterfowl. This may well be the case 
in regions where its abundance is 
measured in thousands of acres. How- 
ever, despite the fact that it formed beds 
of 3 to 81 acres in several [linois River 
valley lakes, none of its seeds were found 
in any of the duck stomachs analyzed, 
table 3. A possible explanation for the 
absence of seeds may be that few were 
available, for in August and September 
thousands of red-winged blackbirds 
were observed feeding on the ripening 
seed. Seeds that escape the blackbirds 
may be inaccessible among the vegeta- 
tion debris and muck of the lake bot- 
Fig. 15.—American lotus (Ne/umbo lutea), or 
yorkey nut as it is often called locally, is seldom 
utilized by ducks despite its abundance. Its 
low value as a food plant is due probably to the 
unpalatability of its hard, nutlike seeds. 
